Not sure where you got 12.6 from, since the current version is 9.4 (typo?), but certainly you can update if you need any new features added since your version, or if you have any encountered any bugs in the old version. If everything is working in your current software, then there is always a risk with updating (that it could accidentally break existing functionality), so it's up to you to decide whether or not that risk is acceptable.

For VB6, you should use the 32-Bit ActiveX version of the library (64-bit is not compatible with VB6).